This invention relates to an excavating tooth and more particularly to a novel point portion thereof, being an improvement on U.S. Pat. No. 4,761,900 which, in turn, was an improvement on co-owned U.S. Pat. No. 4,353,532.
In the '900 patent, a novel locking system was provided to replace the U-shaped fastener employed in the HELILOK.RTM. tooth sold throughout the world--see '532 patent. The '900 system employed a drive through pin maintained in place by a plug member or keeper which extended transversely of the adapter length, i.e., horizontally so as to be unstressed by impact loads. The vertical locking pin in the '900 patent was clamped in place by an ear lug on the point rear cooperating with a pair of vertically spaced ears on the adapters. These cooperated to retain the pin which was generally arched rearwardly, i.e., the convex side faced rearwardly.
I have determined that a significant improvement in operation can be achieved by employing a pair of vertically spaced ear lugs on the point ear, notwithstanding the pin convexity.
Through employing the spaced ear lugs on the point, a point and nose assembly configuration providing improved service life of the nose has been created. In explanation, the end of service life of any excavating tooth system nose is determined most commonly by one or the other of two types of failures:
1. Failure of the nose to retain points, which has been brought about by a wearing away of the nose through service to create a fit of points on the nose that is so loose that the points either fall off or break off.
2. Structural failure of the nose in a fatigue mode. The improved nose service life provided by the inventive point and nose construction results from reductions in the causes of both types of failures.
With regard to nose wear, the inventive construction reduces bearing pressures of the point on the nose by providing a longer bearing surface, thereby slowing the rate of nose wear and resultant loosening of point fits. Also, it provides for a "rocking" type bearing of the point retaining pin against the nose to reduce wear of the pin bearing surface on the nose. Whereas the '900 pin is caused to rub against the nose ears through small movements up and down that are induced by the point under loading, the spaced ear lugs of the inventive point permit a pin configuration that can absorb the point induced movement through rocking. This rocking movement equates to a slower rate of wear on the pin bearing surface of the nose in comparison to the '900 construction, as with the simple analogy of the rolling wheel versus the sliding block. Further the inventive construction provides that the rear sidewalls of the point completely protect the nose pin bearing surface and the pin itself from all external wear, that is, wear from abrasive soil and rock which the tooth system is excavating.
It is axiomatic that a tight fit is desired to keep the point in place on the adapter--this notwithstanding the fact that under high impact loads there is movement of the point relative to the adapter nose (see U.S. Pat. Nos. 2,919,506 and 3,079,710), tightness is relative. The basic HELILOK tooth system of U.S. Pat. No. 4,335,543 is capable of supporting and retaining points on the nose after a considerable amount of looseness has developed from nose wear. It is superior to other tooth systems in this respect, as are the '900 tooth system and the inventive tooth system. Yet, there is a threshold of looseness, which will vary inversely with the severity of application, beyond which a given tooth system will not be capable of supporting and retaining points. It is the extension of the amount of service before this threshold is reached toward which the inventive tooth is directed.
With regard to nose fatigue failures, the use of spaced apart ear lugs on the point permits elimination of projecting ears on the nose. Such projecting ears can be a source of stress concentration. Hence their elimination provides greater nose fatigue strength as well as allowing a longer bearing surface. These two advantages more than compensate for the slight loss of material in the nose to provide the groove for the new side lock pin.
The principal advantages reside in the achievement of heretofore unrealizable tighter fits throughout the adapter life and the avoidance of stress concentrations at the critical juncture of the nose with the shank portion of the adapter while achieving a greater point to nose bearing length.
Points with vertically spaced rearwardly extending ear-like portions have been used previously, as in my prior U.S. Pat. No. 4,326,348 where the ear function was for stabilization in cooperation with a ear cap.
The prior art does not teach the advantageous function of the spaced-apart rearwardly extending ear means in confining the locking pin in original locked position.